1. Field of the Invention
Aspects of the present invention relate to a fuel cell, a fuel cell system, and a method of operating the same.
2. Description of the Related Art
A fuel cell is an electricity generation device that directly converts the chemical energy of hydrogen, included in a hydrocarbon material, such as, methanol, ethanol, or natural gas, into electrical energy through a chemical reaction with oxygen.
A polymer electrolyte membrane fuel cell (PEMFC) has a wide range of applications, for example, as a power source for automobiles, as a distributional power source for houses or public buildings, and as a small power source for electronic devices. A PEMFC has a superior power output, as compared to other fuel cells, a low operating temperature, a rapid start-up, and a short response time.
A conventional PEMFC mainly operates at a temperature below 100° C., for example, at approximately 80° C., to prevent the drying of a polymer electrolyte membrane included therein. However, a conventional PEMFC has problems, due to the low operating temperature of approximately 100° C., or less. For example, a conventional PEMFC uses a hydrogen-rich gas as a fuel, which is obtained by reforming an hydrocarbon containing material, such as, natural gas or methanol, which produces CO2 and CO as by-products. The CO poisons a catalyst included in a cathode and anode of a conventional PEMFC. When the catalyst is poisoned by CO, an electrochemical activity of the catalyst is greatly reduced, and as a result, the operation efficiency and lifetime of the PEMFC are significantly reduced. Furthermore, as the operating temperature of a conventional PEMFC is decreased, the catalyst poisoning by the CO is increased.
A conventional high temperature PEMFC operates at a higher operating temperature of, for example, approximately 130° C., or higher, in order to reduce the poisoning of the catalyst by CO, and to allow for easier temperature control thereof. However, a conventional high temperature PEMFC requires a cooling system to cool a fuel cell stack thereof. The cooling system mainly uses de-ionized water as a coolant.
In a conventional high temperature PEMFC that uses a coolant, an internal temperature of a fuel cell stack must be brought to, for example, 120° C., when the fuel cell stack begins operation. To do this, the coolant that passes through the fuel cell stack must also be heated. However, due to the time required for the coolant to be heated, the normal operation of the PEMFC is delayed.